EP1312885A2 - Heat exchange tube structured on both sides and process for making same - Google Patents

Abstract

The heat exchange tube (1) has outer fins (3) and inner fins (20) crossed by secondary grooves (22) Two rolling tools (11, 12) form the outer fins, and the inner fins are formed by two differently shaped rolling mandrels (15, 16), one forming the inner fins themselves, the other forming the secondary grooves in them.

Description

The invention relates to metallic heat exchanger tubes structured on both sides, in particular finned tubes, according to the preamble of claim 1.

State of the art

Heat transfer occurs in many areas of refrigeration and air conditioning technology as well as in Process and energy technology. For heat transfer in these areas tubular heat exchangers are frequently used. Flows in many applications a liquid on the inside of the tube, depending on the direction of the Heat flow is cooled or heated. The heat is on the outside of the pipe existing medium is released or withdrawn from it. It's state the technology that in tube bundle heat exchangers instead of smooth tubes on both sides structured pipes are used. This will heat up intensified on the inside of the pipe and on the outside of the pipe. The transferred heat flow density is increased and the heat exchanger can be made more compact. Alternatively, the heat flow density can be maintained and the driving temperature difference be lowered, thereby making energy transfer more efficient is possible.

Have structured heat exchanger tubes for shell-and-tube heat exchangers usually at least one structured area and smooth end pieces and possibly smooth intermediate pieces. Limit the smooth end or intermediate pieces the structured areas. So that the tube can be easily inserted into the tube bundle heat exchanger can be installed, the outer diameter of the structured Areas should not be larger than the outer diameter of the smooth end and intermediate pieces.

Integrally rolled finned tubes are often used as structured heat exchanger tubes used. Under integrally rolled finned tubes are finned tubes understood, in which the ribs made of the wall material of a smooth tube were formed. Finned tubes have a ring or screw shape on the outside circumferential ribs. In many cases they have one on the inside of the pipe Variety of axially parallel or helical circumferential ribs that the Improve the heat transfer coefficient on the inside of the pipe. These inner ribs run with a constant cross section parallel to the pipe axis or in the form of Helical lines at a certain angle to the pipe axis. The higher the inner ribs the greater the improvement in the heat transfer coefficient. The manufacture of such pipes is e.g. described in DE 23 03 172. Here is important that through the use of a profiled Rolling mandrel to produce the inner ribs the dimensions of the inner and the External structure of the finned tube can be adjusted independently. This allows both structures to be adapted to the respective requirements and so the tube can be optimally designed.

Many possibilities have been developed recently, depending on the application Heat transfer on the outside of integrally rolled finned tubes continues to increase increase by the ribs on the outside of the tube with further structural features be provided. For example, in the case of condensation of refrigerants on the

Pipe outside the heat transfer coefficient increased significantly when the fin flanks can be provided with additional convex edges (US 5,775,411). at Evaporation of refrigerants on the outside of the pipe has been shown to increase performance proved that the channels between the ribs partially closed seal, so that cavities are created, which are created by pores or slots with the Environment are connected. In particular, such are essentially closed Channels by bending or folding the rib (US 3,696,861, US 5,054,548), by splitting and compressing the rib (DE 2,758,526, US 4,577,381), and by notching and compressing the rib (US 4,660,630, EP 0.713.072, US 4.216.826).

The performance improvements mentioned on the outside of the pipe result in that the majority of the total thermal resistance is on the inside of the pipe is moved. This effect occurs particularly at low flow speeds on the inside of the pipe - e.g. in partial load operation - on. Around So it is to significantly reduce the total thermal resistance necessary to further increase the heat transfer coefficient on the inside of the pipe increase. In principle, this would be by increasing the height of the inner ribs possible, however, due to the increasing, strong deformation of the material is technically difficult to control and furthermore to a high weight of the structured Rohres leads. However, this is undesirable for cost reasons.

Task:

The object of the invention is to provide heat exchanger tubes structured on both sides to produce performance-enhanced internal structure, the weight percentage of Internal structure of the total weight of the pipe must not be higher than that of conventional, helical inner ribs of constant cross-section. The dimensions the inner and outer structure of the finned tube must be independent of each other be adjustable.

Brief description of the invention:

The object is achieved according to the invention in a heat exchanger tube of the type mentioned, in which adjacent inner fins are separated by a primary groove running parallel to the inner fins,
that the inner ribs are crossed by secondary grooves running at a pitch angle β, measured against the pipe axis,
that the secondary grooves run at an angle of inclination y of at least 10 ° with respect to the inner ribs and
that the depth T of the secondary grooves is at least 20% of the rib height H of the inner ribs.

Due to the introduction of the secondary grooves, the inner ribs now have no constant Cross section more. If you follow the course of the inner ribs, then changes the cross-sectional shape of the inner ribs at the locations of the secondary grooves. Through the Secondary grooves create additional vortices in the medium flowing on the pipe side area close to the wall, which increases the heat transfer coefficient. It is realizes that by adding secondary grooves the weight fraction of the Internal structure on the total weight of the pipe is not increased.

The depth of the secondary grooves is radial from the top of the inner rib Direction measured. The depth of the secondary grooves is at least 20% of the height the inner ribs. If the depth of the secondary grooves is equal to the height of the inner ribs then there are structural elements spaced apart on the inside of the tube, the truncated pyramids are similar.

Claims 2 to 13 relate to preferred embodiments of the invention Heat exchanger tube.

The invention further relates to a method according to claims 14 to 19 for the production of the heat exchanger tube according to the invention.

According to the invention is used to produce a heat exchanger tube structured on both sides with the proposed secondary grooves in the internal structure Tool for forming the outer ribs in at least two spaced apart Roll plate packages built. The interior structure is different by two profiled mandrels shaped. The first roll dome supports the pipe in the first forming area under the first roll plate package and forms first Helical circumferential or axially parallel inner ribs, these Internal ribs initially have a constant cross section. The second dome supports the pipe in the second forming area under the second roll plate package larger diameter and forms the secondary grooves according to the invention in the previously formed helically surrounding or axially parallel ribs. The depth The secondary grooves are essentially determined by the choice of the diameter of the two Rolling mandrels set.

Detailed description:

The invention is explained in more detail using the following exemplary embodiments:

Fig.1:

schematisch die Herstellung eines erfindungsgemäßen Wärmeaustauscherrohres mittels zweier Dome mit unterschiedlicher Orientierung der Drallwinkel;

Fig.2:

eine Teilansicht eines erfindungsgemäßen Wärmeaustauscherrohrs, bei dem sich die Sekundärnuten über die gesamte Höhe der Innenrippe ausdehnen, so dass pyramidenstumpfartige Elemente als Innenstruktur erzeugt werden. Die Ansicht ist teilweise als Schnitt dargestellt;

Fig.3:

ein Foto einer Innenstruktur, bei der sich die Sekundärnuten nur über einen Teil der Höhe der Innenrippe erstrecken;

Fig.4:

schematisch einen Schnitt durch die Innenstruktur von Fig. 3 entlang der Linie X-X von Fig. 3;

Fig.5:

ein Diagramm, das den Leistungsvorteil durch die Sekundärnuten der Innenstruktur dokumentiert;

It shows:

Fig.1:

schematically the production of a heat exchanger tube according to the invention by means of two domes with different orientation of the helix angle;

Figure 2:

a partial view of a heat exchanger tube according to the invention, in which the secondary grooves extend over the entire height of the inner rib, so that truncated pyramid-like elements are produced as the inner structure. The view is partially shown as a section;

Figure 3:

a photo of an inner structure in which the secondary grooves extend only over part of the height of the inner rib;

Figure 4:

schematically shows a section through the inner structure of Figure 3 along the line XX of Fig. 3.

Figure 5:

a diagram documenting the performance advantage through the secondary grooves of the inner structure;

The integrally rolled finned tube 1 according to Figures 1 and 2 has on the outside of the tube helically surrounding ribs 3. The preparation of the invention Finned tube is made by a rolling process (see US Pat. No. 1,865,575 / 3.327.512 and DE 23 03 172) by means of the device shown in Figure 1.

A device is used which consists of n = 3 or 4 tool holders 10 consists, in each case at least two spaced-apart rolling tools 11 and 12 are integrated. (In Fig. 1 there is only one tool holder for reasons of clarity 10. The axis of the tool holder 10 is also the Axis of the two associated rolling tools 11 and 12 and it runs obliquely to Tube axis. The tool holder 10 are each offset by 360 ° / n on the circumference of the Finned tube arranged. The tool holder 10 are radially adjustable. they are in turn arranged in a stationary roller head (not shown). The roller head is fixed in the basic structure of the rolling device. The rolling tools 11 and 12 each consist of several roller disks 13 or 14, the diameter of which increases in the direction of the arrow. The rolling disks 14 of the second Rolling tool 12 consequently have a larger diameter than the rolling disks 13 of the first rolling tool 11.

Also part of the device are two profiled mandrels 15 and 16, with the help of which the inner structure of the pipe is produced. The mandrels 15 and 16 are attached to the free end of a rod 9 and rotatably mounted to each other. The Rod 9 is attached at its other end to the basic structure of the rolling device. The rolling mandrels 15 and 16 are closed in the working area of the rolling tools 11 and 12 position. The rod 9 must be at least as long as the one to be manufactured Finned tube 1. Before machining, the smooth tube 2 is in the case of undelivered rolling tools 11 and 12 almost completely on the mandrels 15 and 16 on the Rod 9 pushed. Only the part of the smooth tube 2, that in the finished finned tube 1 is to form the first smooth end piece, is not on the mandrels 15 and 16 pushed.

To process the pipe, the rotating ones arranged on the circumference are used Rolling tools 11 and 12 are fed radially to the smooth tube 2 and with the smooth tube 2 engaged. The smooth tube 2 is thereby rotated. Since the The axis of the rolling tools 11 and 12 is inclined to the tube axis, form the Rolling tools 11 and 12 helical ribs 3 from the Tube wall of the smooth tube 2 and simultaneously push the resulting finned tube 1 corresponding to the slope of the helical circumferential ribs 3 in Direction of arrow. The ribs 3 preferably run like a multi-start thread around. The distance between the centers of two neighboring measured along the pipe axis Ribs is called the rib pitch p. The distance between the two Rolling tools 11 and 12 must be adapted so that the rolling disks 14 of the engage the second rolling tool 12 in the grooves 4, which are between those of the first Rolling tool 11 are formed ribs 3a. Ideally this distance is one integer multiple of the rib division p. The second rolling tool 12 then leads the further formation of the outer ribs 3 continues.

In the forming zone of the first rolling tool 11 (= first forming area) Pipe wall supported by a first profiled rolling mandrel 15, and in the Forming zone of the second rolling tool 12 (= second forming area) Pipe wall supported by a second profiled mandrel 16. The axes the two mandrels 15 and 16 are identical to the axis of the tube. The Rolling mandrels 15 and 16 are profiled differently and the outer diameter of the second rolling mandrel 16 is at most as large as the outer diameter of the first Rolling mandrel 15. Typically, the outer diameter of the second rolling mandrel is 16 up to 0.8 mm smaller than the outside diameter of the first mandrel 15. Das The profile of the rolling mandrels usually consists of a large number of trapezoidal ones or almost trapezoidal grooves that are parallel to each other on the outer surface of the Rolling mandrel are arranged. The one between two adjacent grooves Material of the rolling mandrel is referred to as web 19. The webs 19 have a essential trapezoidal cross-section. The grooves usually run underneath a swirl angle of 0 ° to 70 ° to the axis of the mandrel. At the first mandrel 15 this helix angle is designated by α, in the second rolling mandrel 16 by β.

Twist angle 0 ° corresponds to the case that the grooves are parallel to the axis of the mandrel run. If the twist angle is different from 0 °, the grooves run helically. Helical grooves can be left-handed or right-handed be oriented. 1 and 2 show the case where the first Rolling mandrel 15 right-hand grooves 17 and the second rolling mandrel 16 left-hand grooves 18 has. In this case one speaks of oppositely oriented grooves 17 and 18 or of different orientation of the two swirl angles α and β. In this case the twist angles α and β can have the same amounts. (The same applies to the case that the first rolling mandrel 15 left-handed grooves 17 and the second rolling mandrel 16 right-hand grooves 18.) However, it is also possible that both mandrels 15 and 16 have grooves 17 and 18 with the same orientation. In this case However, the twist angles α and β must differ with regard to their amount. The two mandrels 15 and 16 must be rotatably supported with respect to one another.

Due to the radial forces of the first rolling tool 11, the material of the Pipe wall pressed into the grooves 17 of the first mandrel 15. This will Helical circumferential inner ribs 20 on the inner surface of the finned tube 1 shaped. Primary grooves run between two adjacent inner ribs 20 21. According to the shape of the grooves 17 of the first mandrel 15, these have Inner ribs 20 have a substantially trapezoidal cross section, which initially remains constant along the inner rib. The inner ribs 20 are opposite to the Pipe axis inclined by the same angle α (pitch angle) as the grooves 17 to Axis of the first rolling mandrel 15. The pitch angle of the inner ribs 20 is therefore equal to the twist angle α of the first rolling dome 15. The height of the inner ribs 20 becomes denoted by H and is usually 0.15 - 0.40 mm.

The inner ribs 20 are caused by the radial forces of the second rolling tool 12 pressed onto the second mandrel 16. Since the grooves 18 of the second rolling mandrel 16 at a different angle to the dome axis and thus at a different angle to the Pipe axis run as the grooves 17 of the first mandrel 15, meet the inner ribs 20 in sections on a groove 18 or a web 19 of the second rolling mandrel 16. In the sections in which an inner rib 20 meets a groove 18, the Material of the inner rib 20 pressed into the groove. In the sections where one Inner rib 20 meets a web 19, the rib material is deformed and it become parallel grooves 22 in the inner ribs 20th imprinted. Have according to the shape of the webs 19 of the second mandrel 16 the secondary grooves 22 have a trapezoidal cross section. Secondary grooves 22 by same web 19 are impressed in different inner ribs 20 are each other arranged in alignment. The pitch angle that the secondary grooves 22 with the Form tube axis is equal to the twist angle β, which the grooves 18 of the second mandrel Include 16 with the axis of the second mandrel 16. The angle of inclination y, which the secondary grooves 22 enclose with the inner ribs 20, results in the case of rolling mandrels 15 and 16 with the grooves 17 and 18 oriented in the same direction the difference of the twist angles α and β, with rolling mandrels 15 and 16 with opposite directions Orientation of the grooves 17 and 18 from the sum of the twist angles α and β. The Angle γ is at least 10 °, typically it is in the range between 30 ° and 100 °, preferably between 60 ° and 85 °. Angles y smaller than 90 ° are production-related easier to control than angle y greater than 90 ° and usually cause a smaller pressure drop than angle y greater than 90 °.

The depth T of the secondary grooves 22 is from the tip of the inner rib 20 in radial direction measured. By suitable choice of the outer diameter of the two mandrels 15 and 16, and by suitable choice of the outer diameter the largest rolling disks of the two rolling tools 11 and 12 can Depth T of the secondary grooves 22 can be varied: the smaller the difference in the outer diameter between the first mandrel 15 and the second mandrel 16, the greater the depth T of the secondary grooves 22. A change in the outer diameter of one of the two mandrels 15 or 16 does not have only one Changes in the depth T of the secondary grooves 22 result, but usually causes also a change in the height of the outer ribs 3. This effect can However, can be compensated for by the construction of the rolling tools 11 and 12th modified. In particular, the largest rolling disks 13 of the first can be used for this Rolling tool 11 as the smallest rolling disks 14 of the second rolling tool 12 or the smallest rolling disks 14 of the second rolling tool 12 as the largest Rolling disks 13 of the first rolling tool 11 are used.

In order to significantly influence the flow of the liquid flowing in the tube, should the depth T of the secondary grooves 22 is at least 20% of the height H of the inner ribs 20 be. T is preferably at least 40% of the height H of the inner ribs 20. If the depth T of the secondary grooves 22 is less than the height H of the inner ribs 20, then the course of the inner fins 20 can still be seen on the finely shaped finned tube 1. This is shown in FIG. 3. Changed along the course of the inner ribs 20 but now the cross-sectional shape of the inner ribs 20: the height of the inner ribs 20 is reduced by the depth T at the locations of the secondary grooves 22. The primary grooves 21 run between the inner ribs 20 without interruption Secondary grooves 22 are spaced apart by the primary grooves 21.

Fig. 4 shows schematically a section through the inner structure of Fig. 3 along the Line X-X of FIG. 3. The height relationships between inner ribs 20, primary grooves 21 and secondary grooves 22 can be clearly seen here.

If the depth T of the secondary grooves 22 is equal to the height H of the inner ribs 20, then the shape of the inner fins 20 on the finely shaped finned tube 1 no longer increases detect. The inner ribs 21 are in this case by the secondary grooves 22 in individual, spaced apart elements 23 divided. This is shown in Fig. 2. Due to the trapezoidal cross-section of the initially formed inner ribs 20 and the secondary grooves 22, the spaced elements 23 have the shape of truncated pyramids.

The density of the intersections of inner ribs 20 and secondary grooves 22 is determined by profiling the two rolling mandrels 15 and 16. The density of the intersection points is preferably between 90 and 250 intersection points per cm ² . The inner pipe surface, which results if the inner structure was completely removed from the pipe, serves as a reference surface.

Through the secondary grooves 22, the inner structure of the finned tube 1 with additional Edges. Then liquid flows on the inside of the tube At these edges, additional vortices arise in the liquid, which increase the heat transfer improve on the pipe wall. Usually the pressure drop in the Pipe flowing liquid to the same extent as the heat transfer coefficient. By a suitable choice of the dimensions of the inner structure, in particular the Inclination angle y and the depth T of the secondary grooves 22, this increase in Pressure drop can be influenced favorably.

The description of the manufacturing method according to the invention shows that by the large number of tool parameters that can be selected with this method, the dimensions the external and internal structure are largely independent of each other can be adjusted. In particular, the division of the rolling tool enables into two spaced rolling dies 11 and 12 the depth T of the secondary grooves 22 to vary without changing the height of the outer ribs 3 at the same time.

Finned tubes structured on both sides for refrigeration and air conditioning technology are often made of copper or copper alloys. Since with these metals the pure material price causes a not inconsiderable share of the total cost of the finned tube, the competition requires that the weight of the tube is as low as possible for a given tube diameter. The weight proportion of the inner structure in relation to the total weight in today's commercially available finned tubes is 10% to 20% depending on the height of the inner structure and thus depending on the performance. Due to the secondary grooves 22 according to the invention in the inner fins 20 of finned tubes structured on both sides, the performance of such tubes can be increased considerably without increasing the proportion by weight of the inner structure. In the case of finned tubes, which consist of materials with a density of 7.5 to 9.5 g / cm ³ (for example copper, copper alloys or steel), the weight fraction of such an internal structure, based on the outer envelope surface of the finned tube, is usually between 500 g / m ² and 1000 g / m ² , preferably between 600 g / m ² and 900 g / m ² . In the case of finned tubes, which consist of materials with a density of 2.5 to 3.0 g / cm ³ (for example aluminum), the weight fraction of such an internal structure, based on the outer envelope surface of the finned tube, is usually between 150 g / m ² and 300 g / m ² , preferably between 180 g / m ² and 270 g / m ² . If the width of the primary grooves 21 and the secondary grooves 22 is chosen to be large, then the internal structure can be made light in weight.

5 shows a diagram that documents the performance advantage of the internal structure according to the invention. The heat transfer coefficient is plotted against the heat flow density in the case of condensation of refrigerant R-134a on the outside of the pipe and cooling water flow on the inside of the pipe. The condensation temperature is 36.7 ° C, the water speed 2.4 m / s. The two finned tubes compared have the same structure on the outside, but differ in the internal structure, as indicated in the diagram. The state of the art is represented by the tube, which is provided with a standard internal structure with a height of 0.35 mm. In the finned tube according to the invention with an internal structure with truncated pyramids similar to FIG. 2, the height of the truncated pyramids is approximately 0.30 mm, the density of the intersections of the inner ribs 20 and secondary grooves 22 is 143 per cm ² and the angle γ is 96 °. The finned tube with an inner structure with truncated pyramids has an advantage in the heat transfer coefficient of 13% to 22%. This advantage is due to the internal structure alone, since the heat transfer coefficient on the outside of the pipe is the same for both pipes.

The use of inner fins with secondary grooves to improve heat transfer on the inside of heat exchanger tubes is known from tubes, which only have an internal structure. With seamless pipes, such Internal structures made using two differently shaped mandrels (e.g. JP-OS 1-317637). So far, this technology is only used on the outside of the pipe smooth pipes used. The transfer of this technology to bilaterally structured, integrally rolled finned tubes is, however, due to the significantly different Manufacturing process not obvious: For pipes that are smooth on the outside of the pipe the radial force required to create the internal structure is created Relatively wide rolls, rollers or balls arranged on the outside of the pipe applied. The advance of the pipe in the longitudinal direction of the pipe is here by a separate pulling device accomplished. In contrast, at both sides structured, integrally rolled finned tubes both the radial force for simultaneous Formation of the outer and inner structure as well as the axial force for propulsion of the pipe through the rolling tool, which is built up from relatively thin rolling disks is done alone. The most powerful, commercially available finned tubes are manufactured with rolling disks, whose thickness is between 0.40 mm and 0.65 mm is.

Claims (19)

Heat exchanger tube (1) with optionally smooth ends, at least one structured area on the inside and outside of the tube and optionally smooth intermediate areas, which has the following features: a) integral outer ribs (3) run around helically on the outside of the tube, b) on the inside of the tube, integral inner ribs (20) run axially parallel or helically at a pitch angle α = 0 to 70 ° (measured against the tube axis) to form primary grooves (21), characterized in that c) that the inner ribs (20) are crossed by secondary grooves (22) running at a pitch angle β - measured against the pipe axis - d) that the secondary grooves (22) with respect to the inner ribs (20) run at an inclination angle γ of at least 10 ° and e) that the depth T of the secondary grooves (22) is at least 20% of the rib height H of the inner ribs (20). Heat exchanger tube according to claim 1, characterized in that the angle of inclination y = 30 to 100 °. Heat exchanger tube according to claim 2, characterized in that the angle of inclination y = 60 to 85 °. Heat exchanger tube according to one or more of Claims 1 to 3, characterized in that with inner ribs (20) and secondary grooves (22) running in opposite directions, the angle of inclination y results as the sum of the angle of inclination α and β: γ = α + β. Heat exchanger tube according to one or more of claims 1 to 3, characterized in that with inner ribs (20) and secondary grooves (22) running in the same direction, the angle of inclination y results as the difference between the angles of inclination α and β: γ = α - β. Heat exchanger tube according to one or more of claims 1 to 5, characterized in that the depth T of the secondary grooves (22) is at least 40% of the fin height H. Heat exchanger tube according to one or more of claims 1 to 6, characterized in that the fin height H = 0.15 to 0.40 mm. Heat exchanger tube according to one or more of claims 1 to 7, characterized in that the density of the intersection points of inner ribs (20) and secondary grooves (22) is 90 to 250 intersection points / cm ² . Heat exchanger tube according to one or more of claims 1 to 7, characterized in that the depth T of the secondary grooves (22) corresponds to the fin height H. Heat exchanger tube according to claim 9, characterized in that the inside of the tube has a structure of truncated pyramids (23). Heat exchanger tube according to one or more of claims 1 to 10, characterized in that the weight fraction of the inner structure based on the outer envelope surface of the heat exchanger tube (1) is 500 to 1000 g / m ² , preferably 600 to 900 g / m ² , and that Density of the material used is 7.5 to 9.5 g / cm ³ . Heat exchanger tube according to one or more of claims 1 to 10, characterized in that the proportion by weight of the inner structure related to the outer envelope surface of the heat exchanger tube (1) is 150 to 300 g / m ² , preferably 180 to 270 g / m ² , and that Density of the material used is 2.5 to 3.0 g / cm ³ . Heat exchanger tube according to one or more of claims 1 to 12, characterized in that it is designed as a seamless tube. Method for producing a heat exchanger tube (1), according to one or more of claims 1 to 13, with integral outer fins (3) and inner fins (20) and inner fins (20), which are screwed circumferentially on the outside of the tube and axially parallel or helically extending on the inside of the tube. , which are crossed by secondary grooves (22), in which the following method steps are carried out: a) on the outside of a smooth tube (2) are formed in a first forming area helically extending outer ribs (3) by the rib material is obtained by displacing material from the tube wall by means of a first rolling step and the resulting rib tube (1) by the rolling forces in Offset rotation and is advanced according to the resulting helical ribs (3), the outer ribs (3) being formed from the otherwise undeformed smooth tube (2) with increasing height, b) the tube wall is supported in the first forming area by a first rolling mandrel (15) which is in the tube and which is rotatable and profiled, c) in a second rolling step, the outer ribs (3) are formed with a further increasing height in a second forming area spaced apart from the first forming area and the inner ribs (20) are provided with secondary grooves (22), wherein d) the pipe wall in the second forming area is supported by a second rolling mandrel (16) lying in the pipe, which is also rotatable and profiled, but the profiling of which differs from the profiling of the first rolling mandrel (15) with regard to the amount or the orientation of the helix angle , A method according to claim 14, characterized in that the distance between the forming areas is chosen essentially as an integral multiple of the fin pitch p. A method according to claim 14 or 15, characterized in that the outer diameter of the second rolling mandrel (16) is chosen to be smaller than the outer diameter of the first rolling mandrel (15). Method according to one or more of Claims 14 to 16 for producing a heat exchanger tube (1) according to Claim 4, characterized in that rolling mandrels (15, 16) with grooves (17, 18) oriented in opposite directions are used. Method according to one or more of Claims 14 to 16 for producing a heat exchanger tube (1) according to Claim 5, characterized in that rolling mandrels (15, 16) with grooves (17, 18) oriented in the same direction are used. Method according to one or more of claims 14 to 18, characterized in that the depth T of the secondary grooves (22) by choice of the diameter of the rolling mandrels (15, 16) and by choice of the diameter of the respective largest rolling disks of the two rolling tools (11, 12 ) is set.

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